Local sensing with the multilevel ac Stark effect
Local sensing with the multilevel ac Stark effect
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DOI：
10.1103/physreva.97.062334
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发表时间：
2018-06-22
影响因子：
2.9
通讯作者：
Weides, Martin
中科院分区：
文献类型：
--
作者：
Schneider, Andre;Braumueller, Jochen;Weides, Martin
如果信号电平非常低并且光子能量很不确定，则分析GHz范围内的弱微波信号是一项具有挑战性的任务。超导量子比特可以在低光子状态下检测信号，但由于其离散能级结构，它只对某些能量的光子敏感。与此相反，与多能级量子系统（量子点），未知的信号的频率和振幅可以推导出更高的水平交流斯塔克位移。测量精度由信号幅度、其与离散量子点能级结构的失谐以及非谐性给出。我们证明了能量灵敏度在10-3的顺序与超过1 GHz的测量范围。在这里，使用transmon量子比特，我们实验观察到涉及多达三个激发能级的跃迁频率的变化。这些变化与分析电路模型和主方程模拟吻合得很好。对于大的失谐，我们发现的移位与所施加的微波驱动的功率成线性比例。利用这种效应，我们展示了一种功率计，它可以表征从源到样品的微波传输。
Analyzing weak microwave signals in the GHz regime is a challenging task if the signal level is very low and the photon energy widely undefined. A superconducting qubit can detect signals in the low photon regime, but due to its discrete level structure, it is only sensitive to photons of certain energies. With a multilevel quantum system (qudit) in contrast, the unknown signal frequency and amplitude can be deduced from the higher level ac Stark shift. The measurement accuracy is given by the signal amplitude, its detuning from the discrete qudit energy level structure, and the anharmonicity. We demonstrate an energy sensitivity in the order of 10-3 with a measurement range of more than 1 GHz. Here, using a transmon qubit, we experimentally observe shifts in the transition frequencies involving up to three excited levels. These shifts are in good agreement with an analytic circuit model and master equation simulations. For large detunings, we find the shifts to scale linearly with the power of the applied microwave drive. Exploiting the effect, we demonstrated a power meter which makes it possible to characterize the microwave transmission from source to sample.